1. Field of the Invention
The present invention is directed to an apparatus and a method to provide a three phase separator to separate well stream fluid into three phases—liquid hydrocarbon, water (or brine) and gas. In particular, the present invention is directed to an apparatus and method for a three phase separator for separating well stream fluid having a water surge interface slot to accommodate entry of fluid in the event of a water surge.
2. Prior Art
Three phase separators are well known in the energy industry to separate a fluid flow delivered from a subterranean well or wells. It is also known that wells flow at different rates and that the composition of the fluid may vary from time to time. If the producing pressure becomes so low that the well will not produce at a desired flow rate, a variety of artificial lift methods may be employed. In one type of artificial lift method, plunger lift, periodic surges of liquids are produced.
A stream of fluids is delivered from the well. The purpose of the three phase separator is to separate an incoming feed or flow into a gaseous phase and two liquid phases—a lighter liquid phase primarily composed of liquid hydrocarbons and a water phase primarily composed of water or brine. The specific gravity of the hydrocarbon liquid phase is less than the water phase.
The three phase separator may take various configurations, but generally are either classified as horizontal or vertical or some combination thereof. In one design, a vessel extends and is normally horizontal. A cylindrical wall or shell of the vessel has opposed closed ends. The size of the vessel will vary depending on the flow conditions and the desired retention time. The three phases separate generally by gravity with the gaseous phase migrating to the top of the normally horizontal vessel. Below the gaseous phase, the liquid separates into two phases with the liquid hydrocarbon phase above the water phase. The gaseous phase is removed from the separator and is delivered for further processing or is flared-off. The water phase is removed from the separator and may be pumped back into the subterranean formation or otherwise disposed of. The liquid hydrocarbon phase is removed from the separator and is delivered for further processing.
The fluids in the separator are under pressure and valves and sensors may be employed as liquid level control mechanisms to control and remove the liquids. The liquid hydrocarbon phase and the water phase may be separated into compartments within the vessel.
There have been various designs in the past for three phase separators. For example, Polderman (U.S. Pat. No. 6,537,458) shows one example of a three phase separator. If during any time period, the gaseous phase increases, then the liquid level in the separator will go down while the gas level will increase. In the event of a surge or pulse of liquid into the separator, water may be permitted to flow into the separator box or chamber reserved for oil which frustrates the purpose of the three phase separator.
Coggins et al. (U.S. Pat. No. 4,208,196) discloses a horizontal separator in FIG. 1 with baffles to separate the hydrocarbon liquid from water phase.
Accordingly, it would be advantageous to provide an apparatus, method, and system for a three phase separator that may be deployed near the location of a production well or wells while accommodating a wide variety of flow conditions.
It would be advantageous to provide an apparatus, method and system for a three phase separator to accommodate fluid surges or pulses in the level of liquid into a separator.
Additionally, it would be advantageous to provide an apparatus, method and system for a three phase separator that avoids entry of the water phase into the hydrocarbon liquid phase.